Developing with cephadm

There are several ways to develop with cephadm. Which you use depends on what you’re trying to accomplish.

vstart –cephadm

  • Start a cluster with vstart, with cephadm configured

  • Manage any additional daemons with cephadm

  • Requires compiled ceph binaries

In this case, the mon and manager at a minimum are running in the usual vstart way, not managed by cephadm. But cephadm is enabled and the local host is added, so you can deploy additional daemons or add additional hosts.

This works well for developing cephadm itself, because any mgr/cephadm or cephadm/cephadm code changes can be applied by kicking ceph-mgr with ceph mgr fail x. (When the mgr (re)starts, it loads the cephadm/cephadm script into memory.)

MON=1 MGR=1 OSD=0 MDS=0 ../src/ -d -n -x --cephadm
  • ~/.ssh/id_dsa[.pub] is used as the cluster key. It is assumed that this key is authorized to ssh with no passphrase to root@`hostname`.

  • cephadm does not try to manage any daemons started by (any nonzero number in the environment variables). No service spec is defined for mon or mgr.

  • You’ll see health warnings from cephadm about stray daemons–that’s because the vstart-launched daemons aren’t controlled by cephadm.

  • The default image is, but you can change this by passing -o container_image=... or ceph config set global container_image ....

cstart and cpatch

The script will launch a cluster using cephadm and put the conf and keyring in your build dir, so that the bin/ceph ... CLI works (just like with vstart). The script will tear it down.

  • A unique but stable fsid is stored in fsid (in the build dir).

  • The mon port is random, just like with vstart.

  • The container image is$tag where $tag is the first 8 chars of the fsid.

  • If the container image doesn’t exist yet when you run cstart for the first time, it is built with cpatch.

There are a few advantages here:

  • The cluster is a “normal” cephadm cluster that looks and behaves just like a user’s cluster would. In contrast, vstart and teuthology clusters tend to be special in subtle (and not-so-subtle) ways (e.g. having the lockdep turned on).

To start a test cluster:

sudo ../src/

The last line of the output will be a line you can cut+paste to update the container image. For instance:

sudo ../src/script/cpatch -t

By default, cpatch will patch everything it can think of from the local build dir into the container image. If you are working on a specific part of the system, though, can you get away with smaller changes so that cpatch runs faster. For instance:

sudo ../src/script/cpatch -t --py

will update the mgr modules (minus the dashboard). Or:

sudo ../src/script/cpatch -t --core

will do most binaries and libraries. Pass -h to cpatch for all options.

Once the container is updated, you can refresh/restart daemons by bouncing them with:

sudo systemctl restart ceph-`cat fsid`.target

When you’re done, you can tear down the cluster with:

sudo ../src/   # or,
sudo ../src/cephadm/cephadm rm-cluster --force --fsid `cat fsid`

cephadm bootstrap –shared_ceph_folder

Cephadm can also be used directly without compiled ceph binaries.

Run cephadm like so:

sudo ./cephadm bootstrap --mon-ip \
  --ssh-private-key /home/<user>/.ssh/id_rsa \
  --skip-mon-network \
  --skip-monitoring-stack --single-host-defaults \
  --skip-dashboard \
  --shared_ceph_folder /home/<user>/path/to/ceph/
  • ~/.ssh/id_rsa is used as the cluster key. It is assumed that this key is authorized to ssh with no passphrase to root@`hostname`.

Source code changes made in the pybind/mgr/ directory then require a daemon restart to take effect.

Note regarding network calls from CLI handlers

Executing any cephadm CLI commands like ceph orch ls will block the mon command handler thread within the MGR, thus preventing any concurrent CLI calls. Note that pressing ^C will not resolve this situation, as only the client will be aborted, but not execution of the command within the orchestrator manager module itself. This means, cephadm will be completely unresponsive until the execution of the CLI handler is fully completed. Note that even ceph orch ps will not respond while another handler is executing.

This means we should do very few synchronous calls to remote hosts. As a guideline, cephadm should do at most O(1) network calls in CLI handlers. Everything else should be done asynchronously in other threads, like serve().

Note regarding different variables used in the code

  • a service_type is something like mon, mgr, alertmanager etc defined in ServiceSpec

  • a service_id is the name of the service. Some services don’t have names.

  • a service_name is <service_type>.<service_id>

  • a daemon_type is the same as the service_type, except for ingress, which has the haproxy and keepalived daemon types.

  • a daemon_id is typically <service_id>.<hostname>.<random-string>. (Not the case for e.g. OSDs. OSDs are always called OSD.N)

  • a daemon_name is <daemon_type>.<daemon_id>

Kcli: a virtualization management tool to make easy orchestrators development

Kcli is meant to interact with existing virtualization providers (libvirt, KubeVirt, oVirt, OpenStack, VMware vSphere, GCP and AWS) and to easily deploy and customize VMs from cloud images.

It allows you to setup an environment with several vms with your preferred configuration( memory, cpus, disks) and OS flavor.

main advantages:

  • Is fast. Typically you can have a completely new Ceph cluster ready to debug and develop orchestrator features in less than 5 minutes.

  • Is a “near production” lab. The lab created with kcli is very near of “real” clusters in QE labs or even in production. So easy to test “real things” in almost “real environment”

  • Is safe and isolated. Do not depend of the things you have installed in your machine. And the vms are isolated from your environment.

  • Easy to work “dev” environment. For “not compilated” software pieces, for example any mgr module. It is an environment that allow you to test your changes interactively.


Complete documentation in kcli installation but we strongly suggest to use the container image approach.

So things to do:
  • 1. Review requeriments and install/configure whatever you need to meet them.

  • 2. get the kcli image and create one alias for executing the kcli command

    # podman pull
    # alias kcli='podman run --net host -it --rm --security-opt label=disable -v $HOME/.ssh:/root/.ssh -v $HOME/.kcli:/root/.kcli -v /var/lib/libvirt/images:/var/lib/libvirt/images -v /var/run/libvirt:/var/run/libvirt -v $PWD:/workdir -v /var/tmp:/ignitiondir'


/var/lib/libvirt/images can be customized…. be sure that you are using this folder for your OS images


Once you have used your kcli tool to create and use different labs, we suggest you to “save” and use your own kcli image. Why?: kcli is alive and it changes (and for the moment only exists one tag … latest). Because we have more than enough with the current functionality, and what we want is overall stability, we suggest to store the kcli image you are using in a safe place and update your kcli alias to use your own image.

Test your kcli installation:

See the kcli basic usage workflow

Create a Ceph lab cluster

In order to make easy this task we are going to use a kcli plan.

A kcli plan is a file where you can define the different settings you want to have in a set of vms. You can define hardware parameters (cpu, memory, disks ..), operating system and it also allows you to automate the installation and configuration of any software you want to have.

There is a repository with a collection of plans that can be used for different purposes. And we have predefined plans to install Ceph clusters using Ceph ansible or cephadm, lets create our first Ceph cluster using cephadm:

# kcli2 create plan -u

This will create a set of three vms using the plan file pointed by the url. After a few minutes (depend of your laptop power), lets examine the cluster:

  • Take a look to the vms created:

    # kcli list vms
  • Enter in the bootstrap node:

    # kcli ssh ceph-node-00
  • Take a look to the ceph cluster installed:

    [centos@ceph-node-00 ~]$ sudo -i
    [root@ceph-node-00 ~]# cephadm version
    [root@ceph-node-00 ~]# cephadm shell
    [ceph: root@ceph-node-00 /]# ceph orch host ls

Create a Ceph cluster to make easy developing in mgr modules (Orchestrators and Dashboard)

The cephadm kcli plan (and cephadm) are prepared to do that.

The idea behind this method is to replace several python mgr folders in each of the ceph daemons with the source code folders in your host machine. This “trick” will allow you to make changes in any orchestrator or dashboard module and test them intermediately. (only needed to disable/enable the mgr module)

So in order to create a ceph cluster for development purposes you must use the same cephadm plan but with a new parameter pointing your Ceph source code folder:

# kcli create plan -u -P ceph_dev_folder=/home/mycodefolder/ceph

Ceph Dashboard development

Ceph dashboard module is not going to be loaded if previously you have not generated the frontend bundle.

For now, in order load properly the Ceph Dashboardmodule and to apply frontend changes you have to run “ng build” on your laptop:

# Start local frontend build with watcher (in background):
sudo dnf install -y nodejs
cd <path-to-your-ceph-repo>
cd src/pybind/mgr/dashboard/frontend
sudo chown -R <your-user>:root dist node_modules
NG_CLI_ANALYTICS=false npm ci
npm run build -- --deleteOutputPath=false --watch &

After saving your changes, the frontend bundle will be built again. When completed, you’ll see:

"Localized bundle generation complete."

Then you can reload your Dashboard browser tab.